My guild completely relies on dkp, ignoring all priority unless an item simply isnt intelligent for the class or spec to receive. Items go to whoever is in the highest attendance bracket and has most dkp (within 5% or they /roll). We sometimes ask people to pass on an item, but it is not required. The tanks typically just use good judgement before passing an item, but occasionally there is questions of "hey will you pass that to me?" without what I'd call necessity.
I'm from Onyxia, where trade chat makes you wish you were in the barrens.